Sound picture recording system



P 1936-. l. M. CHAMBERS 2,055,654

SOUND PICTURE RECORDING SYSTEM Filed April 14, 1932 3 Sheets-Sheet l QNJMM ATTORNEY Sept. 29, 1936. M. CHAMBERS SOUND PICTURE RECORDING SYSTEM 3 Sheets-Sheet 2 Filed April 14, 1932 FIG. 4

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SOUND PICTURE RECORDING SYSTEM Filed April 14, 1932 Sheets-Sheet 5 FIG. 11

' INVENRDR M. CHAMBERS BY H :11 ATiE/QNEV Patented Sept. 29, 1936 PATENT OFFICE 2,055,654 SOUND PICTURE nscoanmo SYSTEM Irl M. Chambers, Los Angeles, Calif., assignor, by mesne assignments, to Western Electric Company, Incorporated, a corporation of New York Application April 14, 1932, Serial No. 605,258

9 Claims.

This invention relates to sound. recording systems and apparatus and more particularly to such systems in which acoustically'modulated light waves are-recorded on photographic sensi- 5 tive film. I I

In sound recording systems of this type two distinct types of sound records may be produced.

graph mirror is adjusted to illuminate half the sound track when the mirror is at rest and is used to produce this type of record. A third type known in the art is the variable density-variable area record which combines the features of both the aforementioned types and is a desirable form 26 duction. r

The object of this invention is to provide a method and apparatus for producing a sound record varying both in density and in width in accordance with the recorded sound.

A feature of the invention lies in the provision of a light valve in which the movable member or members actuated by sound modulated current are disposed with relation to a fixed slit in such manner as to produce a variable area-variable density sound record.

In accordance with one embodiment of the invention a variable density-variable area sound record is produced by employing a light valve of the type disclosed in the United States Patent 1,638,555, August 9, 1927 to E. C. Wente, the filaments of which are maintained parallel to form a light transmitting slot but are disposed at an angle to a fixed slit. The light valve filaments are supplied with modulated electrical currents, causing them to move relative to each other and permit light rays to pass through the fixed slit on to the film in the form of a parallelogram of limited maximum width in the direction of travel of record to be obtained for sound picture reproarea modulations extending able area-variable density record is produced by employing a light valve having a single filament or movable element disposed ina magnetic field at an angle to a fixed slit. A single filament valve of this type will produce a negative sound track of variable area-variable density modulations extending from one edge of thefilm.

In the drawings Fig. 1 is a plan view of the inner surface of a light valvecasing cover;

Fig. 2 is a side elevation, partly in section, of an assembled light valve taken through line 2-2 of Fig. 1;

Figs. 3, 4, and 5 are enlarged views showing the shape of the light transmitting opening formed through the elongated aperture by the ribbons of a double ribbon light valve in closed, neutral and. open positions, respectively;

Figs. '6, 7, and 8 are enlarged views showing the shape of the light transmitting opening formed through the elongated aperture by the ribbon of a single ribbon light valve in closed, neutral and open positions, respectively;

Fig. 9 is a section of a sound film having thereon a variable area-variable density sound record recorded by means of an oblique double ribbon light valve; Y

Fig. 10 is a section of a sound film having thereon a variable area-variable density sound record recorded by means of an oblique single ribbon light valve; v

Fig. 11 is a diagrammaticanalysis of modulation obtained on a sound film with the ribbons of an oblique double ribbon valve opening from the neutral position; and

Fig. 12 is a diagrammatic analysis of modulation contained on separate areas of a sound film with the ribbons of an oblique double ribbon light valve opening further from the position shown in Fig. 11.

Fig. 13 is a diagrammatic analysis of modulation contained on a sound film when the ribbons of an oblique double ribbon valve are closed from neutral position.

In Fig. 1, a light valve casing cover i has attached thereto on its inner surface one pole piece 2, having an elongated aperture 3 therein. Movable elements or ribbons 4 are located adjacent the aperture in the pole face of pole piece 2. The movable elements 4 forming a lighttransmitting opening are actually formed of one continuous ribbon having one end attached to take-up screw 6. The ribbon is passed diagonally over the pole face of pole piece 2, but free from contact therewith, around a pulley I, back diagonally across the pole piece 2 and terminates in take-up screw 8. These movable elements are held from contact with the pole face of pole piece 2 by means of bridge members 9 and I including frets l I and I2 on which the ribbons rest. These frets are usually ivory strips of a height such that the ribbons resting thereon clear the surface of the pole face. The centers of the bridge members 9 and ID are located on opposite sides of the center line of the elongated aperture 3.

Also attached to the inner surface of the cover on opposite sides of the pole piece 2 are ribbon adjustment members I3 and I4. Since the mem bers i3 and 44 are identical, a description of the former will suffice. The two sides of the member l3 on opposite sides of the movable elements are formed from a single block of some insulating material. Pincer members l5 and I6 mounted in member I 3 are actuated by screw members I! and I8, respectively, to adjust the spacing between the movable elements 4 and also their position on the fret H. By means of these adjustment members the angular position of the ribbons with respect to the elongated aperture 3 may be accurately adjusted.

There is provided, as a means for tensioning the movable elements, a bracket 20 pivoted to the casing cover at 2! and held under tension by a spring 22. Mounted on the bracket is a spring 23 to the bight portion of which is attached an extension bearing the idler or pulley I made of some suitable insulating material. The bracket 20 bears against a conical-shaped cam member 25 arranged to be advanced by a threaded portion cooperating with a threaded hole in the cover I (not shown).

Pole piece spacing members 25 and 21 are attached to the casing cover on opposite sides of pole piece 2. When the light valve is assembled, the ends of these spacing members bear against pole piece 5, (Fig. 2) and are accurately machined to a height exceeding the combined height of the pole pieces an amount sufiicient to allow the proper space between the pole faces. Binding posts 29 and 30 are provided on the exterior of the cover to facilitate connection of the filament circuit to an external source of sound modulating current. Such sound modulating current is applied to the movable elements 4 through conductors 3| and 32 which are connected to the binding posts 29 and 30.

In Fig.- 2, numeral 34 represents a light valve casing containing a field winding 35 and the other pole piece 5. A knurled annular ring 31 provided with an internal screw thread to engage the thread on the circumference of the casing cover, holds the casing cover in assembled position on the casing 34.

As shown in Fig. 2, the pole piece 5 has an aperture therein which is in alignment with the aperture 3 in pole piece 2. Numeral 39 indicates a circular recess into which is placed one end of an objective lens assembly adapted to project an image of a light transmitting slot, formed by the movable elements, to a photographically sensitive film. A light beam from a constant intensity light source is projected to the valve at 40. The beam passes through the light transmitting slot formed by the ribbons 4 and through passage 4| on to a photographically sensitive film (not shown).

Figs. 3, 4, and 5 show enlarged views of the movable elements R1 and R2 of a double string light valve and the angle they make with an elongated aperture A. The angular position of the elements with respect to the aperture must be accurately adjusted as too great an angle would expose the useful part of the sound track on the outside edge of each ribbon when full modulation to closed position occurred. This angle depends upon the modulation, the greater the modulation the greater the angle. Another factor limiting this angle is the widthcf the ribbons R1 and R2. As shown in Fig. 3 the angle is so chosen that for complete modulation of the ribbons R1 and R2 to closed position, no portion of the sound track is exposed to light through the aperture as the movable elements are of such a width that they completely cover the aperture A.

In Fig. 4 the movable elements R1 and R: are shown 'in neutral position or in the position they assume when no acoustically modulated current is passing therethrough. It will be seen that the light transmitting opening produced on the aperture A by the movable elements is in the form of a parallelogram of limited maximum width in the direction of travel of the film and varying in length transversely of the film when the movable elements open at maximum modulation, as shown in Fig. 5. In the latter figure it is seen that for maximum modulation in a direction opposite to that shown in Fig. 3, the length of the light transmitting opening formed on the aperture A by the inside edges of the movable elements does not exceed the fixed length of this elongated aperture. Therefore, the complete modulation of the movable elements in either direction is fully recorded on the photographic film.

Figs. 6, 7, and 8 show enlarged views of the movable element R of a single ribbon light valve and the angle it makes with the elongated aperture A. As in the former case; this angle depends upon the extent of modulation of, and the width of the movable element R. It will be seen in Fig. 6 that for full modulation of the element R in one direction, the outer edge of this element just covers the unexposed end of the aperture A. Also, for full modulation of element R in the other direction, as shown in Fig. 8, the length of the area which would be exposed through an aperture of the width shown does not exceed the length of the aperture A.

In Fig. 9, 50 designates a section of a photographic film having thereon a variable density, variable area sound record 5|, recorded by means of the oblique double ribbon light valve discussed above. It will be seen that the sound track BI is dark in the center with variable density, variable area modulation extending equal distances from the center line of the film.

In Fig. 10, numeral 52 designates a section of photographic film having thereon a variable density, variable area sound record 53 recorded by means of the oblique single ribbon light valve discussed in connection with Figs. 6, '7, and 8. In both Figs. 9 and the sound record is shown as occupying the full width of the film. These sound records, however, may be confined to a small area of film to provide for a combined picture and sound film.

In Fig. 11, disclosing diagrammatically an analysis of the modulations obtained on separate areas of a film with an oblique double ribbon light valve, letter A designates an aperture as in the preceding figures while R1 and R2 represent the inner edges of movable elements of a light valve. It is the case in Fig. 11 that the movable elements are opening from neutral position and in so opening there is formed on the film an area 55 of variable density exposure, area 56 of combined variable density-variable area exposure.

In Fig. 12 there is disclosed diagrammatically an analysis of the modulations obtained on separate areas of a film when the movable elements R1 and R: open further from the position shown in Fig. 11. It will be seen that there is a discontinuity in that the area 55 of variable density exposure in Fig. 11 is no longer modulated and a pure variable area track 51 is produced between the points P1 and P2. The two large triangles 58 and 59 contain the sections of variable density and combined variable density-variable area modulations shown in Fig. 11. Since triangles 58 and 59 remain the same size and density in any position of greater opening than that shown in Fig. 11, their resultant effect is zero.

The movable elements R1 and R: in closing from neutral position as shown in Fig. 13, form on the film an area 60 of variable density exposure, areas H of combined variable density-variable area exposure and areas 62 of variable area exposure.

It has been found that either an oblique double,

ribbon valve or a single ribbon light valve constructed and used as outlined will poduce an improved type photographic sound record wherein all modulations of the movable elements of the light valve are fully recorded in the form of a variable density, variable area sound record.

What is claimed is:

1. A device for recording sound waves which comprises a system for transmitting light from a source to a photographic film, means for varying the amount of transmitted light comprising a member having an elongated slit therein, a pair of electrical conductors arranged in a magnetic field and adjacent the slit in said member to define a light transmitting slot, means for supplying electric currents to said conductors to effect a variation in their space relation, said conductors and said slit member disposed in oblique relation to each other.

2. In combination, a member having a slit therein, a pair of parallel conductors arranged in a magnetic field adjacent the slit in said member to define a light transmitting slot, said conductors disposed in oblique relation to the slit in said member, and means to supply modulated electrical currents to said conductors to effect a variation in their space relation whereby the amountof light transmitted through said slit member is varied.

3. A light valve comprising a frame, a pair of magnets supported by said frame, said magnets having aligned apertures, a pair of parallel eleccal conductors interposed between the adjacent faces of said magnets to define a light transmitting slot, said conductors mounted in oblique relation to the aperture formed in said magnets, and means to supply current to said conductors to vary\their space relation whereby the amount of the light transmitted through said aperture member is varied.

4. A light valve comprising a frame, a pair of magnets supported by said frame, said magnets having aligned apertures, a pair of electrical conductors interposed between the adjacent faces of said magnets in a plane parallel thereto, said conductors mounted parallel to each other but in oblique relation to the aperture in said magnets, means supporting said conductors between said magnets, said means comprising a pair of bridge members carried by said frame at opposite sides of the center line of the aperture in said magnets.

5. A light valve comprising aframe, a pair of magnets supported by said frame, said magnets having aligned apertures, a pair of electrical conductors interposed between the adjacent faces of said magnets to form a light transmitting slot the longitudinal axis of which is disposed at an angle to the longitudinal 'axis of the aperture in said magnets, and means for adjusting the angular position of said conductors with respect to the aperture in said magnets.

6. A light valve comprising a frame, a pair of magnets supported by said frame, said magnets having aligned apertures, a pair of electrical conductors interposed between the adjacent faces of said magnets to form a light transmitting slot the longitudinal axis of which is disposed at an angle to the longitudinal axisof the aperture in said magnets, means for adjusting the angular position of said conductors with respect to the aperture in said magnets, and bridge members carried by said frame for supporting said conductors in their adjusted angular position.

7. In combination, a member having a fixed elongated aperture therein, a movable element suspended in a magnetic field and disposed in oblique relation to the aperture in said member, and means to supply modulated electrical currents to said movable element to effect a movement thereof in front of the aperture in said member.

8. A light valve comprising a frame, a pair of magnets supported by said frame, said magnets having aligned apertures, a movable element suspended between the adjacent faces of said magnets in a plane parallel to said magnet faces but disposed in oblique relation to the aperture therein, and means to supply current to said conductor to effect a movement thereof in said parallel IRL M. CHAMBERS. 

